With the observation that tyrosine-protein kinases are commonly involved in cell growth control, significant effort has been devoted to understanding the identities, distributions and biochemical actions of these kinases. Such research has recently yielded the curious observation that elevated levels of tyrosine kinase activity are not only associated with rapidly growing and transformed cells, but in some cases also with quiescent, terminally differentiated cells. Since information on the roles of tyrosine kinases in nondividing cells might also provide insight into one or more aspects of their activities in transformed cells, we have undertaken an investigation of the regulation of the tyrosine kinase of erythrocytes and its influence on the properties of the major substrate band 3, especially on its ability to bind and regulate glycolytic enzymes. We intend to purify the above kinase and determine which endogenous/exogenous ligands modulate its activity. We also plan to determine whether activation/inhibition of the kinase in vivo regulates erythrocyte metabolism, as suggested from recent in vitro kinase in vivo regulates erythrocyte metabolism, as suggested from recent in vitro studies. Finally, because glycolytic rates and tyrosine kinase activity are often elevated in transformed cells, we plan to investigate the tyrosine phosphorylation of glycolytic enzyme binding proteins in nonerythroid cells in an attempt to understand the role they may play in the regulation of cell metabolism.